Larger Pacific Striped Octopus

"Its eyes are unusual, consisting of stacked layers of lenses that rise like two small towers above its head. ...

"At the top of each eye is an even more unusual feature: a lobe that juts out from the tower. This lobe, the researchers note, offers the stacked lenses protection from stray light from above that might affect its ability to see horizontally across the sea floor. Modern arthropods have avoided this problem by evolving different lens and photoreceptor systems. But for the ancient trilobite, the researchers note, this special eyeshade was the answer."

TONMO Supporter

You know, trilobite eyes were really quite bizarre. Their eyes contained prisms of calcite crystals and operated to a unique system that has not been repeated anywhere else in the animal kingdom. Each facet of the eye contained an elongated crystal pointing in a slightly different direction. It is thought that each prism had a receptor cell at its base in order for the brain to translate the light into an image.

Some trilobites had just one cell but most had dozens and some had thousands, varying from species to species, though a fair number of the earliest species were blind. Most trilobites had eyes that searched forward, sideways and slightly behind but rarely upwards so their vision must have been limited to the seafloor, which has always struck me as a little odd given that I would have expected many of the marine predators to have struck from above. It would be interesting to find out if there is any evidence of predation by nautiloids on trilobites.

Anyone interested in trilobites should find themselves a copy of Richard Fortey’s Trilobite! Eyewitness to Evolution Flamingo, 2000. It is a cracking read.

Thanks for the link. Here’s another link with a photo of the specimen. Great photos, though the page is in German.